The phosphoinositide 3-kinases (PI3 kinases or PI3Ks), a family of lipid kinases, have been found to have key regulatory roles in many cellular processes including cell survival, proliferation and differentiation. As major effectors downstream of receptor tyrosine kinases (RTKs) and G protein-coupled receptors (GPCRs), PI3Ks transduce signals from various growth factors and cytokines into intracellular massages by generating phospholipids, which activate the serine-threonine protein kinase AKT (also known as protein kinase B (PKB)) and other downstream effector pathways. The tumor suppressor or PTEN (phosphatase and tensin homologue) is the most important negative regulator of the PI3K signaling pathway (“Small-molecule inhibitors of the PI3K signaling network.” Future Med Chem., 2011, 3, 5, 549-565).
To date, eight mammalian PI3Ks have been identified, divided into three main classes (I, II and III) on the basis of their genetic sequence, structure, adapter molecules, expression, mode of activation, and preferred substrate. Among them, Class I PI3Ks are further divided based on signaling pathways and regulatory proteins into class IA and class IB. The class IA PI3Ks comprise three closely related kinases, PI3Kα, PI3Kβ, and PI3Kδ, which exist as heterodimers composed of a catalytic subunit (p110α, p110β, and p110δ respectively) and a p85 regulatory adapter subunits (i.e., p85α, p85β, p55δ, p55α and p50α). The catalytic p110 subunit uses ATP to phosphorylate phosphatidylinositol (PI, PtdIns), PI4P and PI (4,5) P2. These respond to signaling generally through receptor tyrosine kinases (RTKs). The class IB PI3Kγ signals through G-protein-coupled receptors (GPCRs) and is composed of a p110γ catalytic domain that can associate with regulatory subunits distinct from the class IA isoforms.
In relation to function and regulation of effector enzymes in phospholipids signaling pathways, class I PI3-kinases (e.g. PI3Kδ, PI3Kdelta) generate second messengers from the membrane phospholipid pools. Class I PI3Ks convert the membrane phospholipid PI(4,5) P2 into PI(3,4,5) P3, which functions as a second messenger. PI and PI(4)P are also substrates of PI3K and can be phosphorylated and converted into PI3P and PI(3,4)P2, respectively. In addition, these phosphoinositides can be converted into other phosphoinositides by 5′-specific and 3′-specific phosphatases. Thus, PI3K enzymatic activity results either directly or indirectly in the generation of two 3′-phosphoinositide subtypes which function as second messengers in intracellular signal transduction pathways (Nature Reviews Molecular Cell Biology, 2010, 11, 329).
Expression of the PI3Kα and PI3Kβ isoforms is ubiquitous, while the expression pattern of PI3Kδ and PI3Kγ seems more restricted, with both isoforms found primarily in leukocytes. The relatively restricted expression pattern of PI3Kδ and PI3Kγ, in addition to data accumulated from studies in mice suggests that these two isoforms play a major role in the adaptive and innate immune systems (J. Med. Chem., 2012, 55, 20, 8559-8581).
In B and T cells, PI3Ks have an important role through activation of the Tec family of protein tyrosine kinases which include Bruton's tyrosine kinase (BTK) in B cells and Interleukin-2-inducible T-cell kinase (ITK) in T cells. Upon PI3K activation, BTK or ITK translocate to the plasma membrane where they are subsequently phosphorylated by Src kinases. One of the major targets of activated ITK is phospholipase C-gamma (PLCγ1), which hydrolyses PI(4,5)P2 into PI(3,4,5)P3 and initiates an intracellular increase in calcium levels and diacylglycerol (DAG) which can activate Protein Kinases C in activated T cells.
The PI3Kδ kinase dead knock-in mice are viable and their phenotype is restricted to defects in immune signaling (Okkenhaug et al., Science, 2002, 297, p. 1031-4). These transgenic mice have offered insight into the function of PI3Kδ in B-cell and T-cell signaling. In particular, PI3Kδ is required for PI(3,4,5)P3 formation downstream of CD28 and/or T cell Receptor (TCR) signaling. A key effect of PI3K signaling downstream of TCR is the activation of Akt, which phosphorylates anti-apoptotic factors as well as various transcription factors for cytokine production. As a consequence, T cells with inactive PI3Kδ have defects in proliferation and TM and Th2 cytokine secretion. Activation of T cells through CD28 lowers the threshold for TCR activation by antigen and increases the magnitude and duration of the proliferative response. These effects are mediated by the PI3Kδ-dependent increase in the transcription of a number of genes including IL2, an important T cell growth factor.
Therefore, PI3K inhibitors are anticipated to provide therapeutic benefit via its role in modulating T-cell mediated inflammatory responses associated to respiratory diseases such as asthma, COPD and cystic fibrosis. In addition, there is indication that T-cell directed therapies may provide corticosteroid sparing properties (Lancet, 1992, 339, p. 324-8) suggesting that it may provide a useful therapy either as a standalone or in combination with inhaled or oral glucocorticosteroids in respiratory diseases. A PI3K inhibitor might also be used alongside other conventional therapies such as long acting beta-agonists (LABA) in asthma.
In the vasculature, PI3Kδ is expressed by endothelial cells and participates in neutrophil trafficking by modulating the proadhesive state of these cells in response to TNFalpha (Blood, 2004, 103, 9, p. 3448). A role for PI3Kδ in TNFalpha-induced signaling of endothelial cells is demonstrated by the pharmacological inhibition of Akt phosphorylation and PDK1 activity. In addition, PI3Kδ is implicated in vascular permeability and airway tissue edema through the VEGF pathway (Allergy Clin. Immunol., 2006, 118, 2, p. 403). These observations suggest additional benefits of PI3Kδ inhibition in asthma by the combined reduction of leukocyte extravasation and vascular permeability associated with asthma. In addition, PI3Kδ activity is required for mast cell function both in vitro and in vivo (Nature, 2004, 431, p. 1007; J. Immunol., 2008, 180, 4, p. 2538) further suggesting that PI3K inhibition should be of therapeutic benefit for allergic indications such asthma, allergic rhinitis and atopic dermatitis.
The role of PI3Kδ in B cell proliferation, antibody secretion, B-cell antigen and IL-4 receptor signaling, B-cell antigen presenting function is also well established (J. Immunol., 2007, 178, 4, p. 2328-35; Blood, 2006, 107, 2, p. 642-50) and indicates a role in autoimmune diseases such as rheumatoid arthritis or systemic lupus erythematosus. Therefore PI3K inhibitors may also be of benefit for these indications.
Pharmacological inhibition of PI3Kδ inhibits fMLP-dependent neutrophil chemotaxis on an ICAM coated agarose matrix integrin-dependent biased system (J Immunol., 2003, 170, 5, p. 2647-54). Inhibition of PI3Kδ regulates neutrophil activation, adhesion and migration without affecting neutrophil mediated phagocytosis and bactericidal activity over Staphylococcus aureus (Biochem. Biophys. Res. Commun, 2003, 308, 4, p. 764-9). Overall, the data suggest that PI3Kδ inhibition should not globally inhibit neutrophil functions required for innate immune defense. PI3Kδ's role in neutrophils offers further scope for treating inflammatory diseases involving tissue remodeling such as COPD or rheumatoid arthritis.
The phosphoinositide 3-kinase 6 subunit (PI3Kδ) isoform is mainly expressed in immune cells and is absent from most solid tumors. Gene targeting in mice has established essential functions for PI3Kδ in mature B cells and in other immune cell types. A key downstream effector of PI3Kδ in B cells is Bruton's tyrosine kinase (BTK), which is a member of the TEC family of non-receptor tyrosine kinases. PI3Kδ and BTK are activated by signals from the B cell receptor (BCR), chemokines and cytokines to drive survival, proliferation and adhesion to supportive stromal cells. However, activating mutations in PI3Kδ is not present in B cell tumors, and inhibitors of these enzymes were initially developed for application in immune diseases. Unexpectedly, Phase I clinical trials of a PI3Kδ inhibitor (CAL-101, renamed GS-1101) showed dramatic and durable responses in a subset of patients with indolent B cell malignancies. Even greater efficacy was achieved in combination studies with rituximab and/or bendamustine. PI3Kδ inhibitors has shown acceptable safety profiles. The compound, now called idelalisib, was approved by US Food and Drug Administration (FDA) to treat chronic lymphocytic leukemia (CLL), follicular B-cell non-Hodgkin lymphoma (FL) and relapsed small lymphocytic lymphoma (SLL). (Nature Review Drug Discovery, 2014, 13, p140-156)
PI3Kγ has been identified as a mediator of G beta-gamma-dependent regulation of JNK activity, and G beta-gamma are subunits of heterotrimeric G proteins (J. Biol. Chem., 1998, 273, 5, p. 2505-8). It has been described that PI3Kγ relays inflammatory signals through various G(i)-coupled receptors and is central to mast cell function, stimuli in the context of leukocytes, and immunology including cytokines, chemokines, adenosines, antibodies, integrins, aggregation factors, growth factors, viruses or hormones for example (Immunity, 2002, 16, 3, p. 441-51; J. Cell Sci., 2001, 114 (Pt 16), p. 2903-10 and Curr. Opinion Cell Biol., 2002, 14, 2, p. 203-13).
It is now well understood that deregulation of oncogenes and tumor suppressor genes contributes to the formation of malignant tumors, for example by way of increased cell growth and proliferation or increased cell survival. It is also now known that signaling pathways mediated by the PI3K family have a central role in a number of cell processes including proliferation and survival, and deregulation of these pathways is a causative factor a wide spectrum of human cancers and other diseases (Annual Rev. Cell Dev. Biol., 2001, 17, p. 615-675 and J. Cell Science, 2003, 116, 15, p. 3037-3040).
There is good evidence that class I PI3K enzymes contribute to tumorigenesis in a wide variety of human cancers, either directly or indirectly (Nature Reviews Cancer, 2002, 2, 7, p. 489-501). For example, inhibition of PI3Kδ may have a therapeutic role for the treatment of malignant haematological disorders such as acute myeloid leukaemia (Oncogene, 2006, 25, 50, p. 6648-59). Moreover, activating mutations within p110α (PIK3CA gene) have been associated with various other tumors such as those of the colon and of the breast and lung (Science, 2004, 304, 5670, p. 554; Nature Reviews Cancer, 2009, 9, 551).
A wide variety of retroviruses and DNA based viruses activate the PI3K pathway as a way of preventing host cell death during viral infection and ultimately exploiting the host cell synthesis machinery for its replication (Virology, 2006, 344, 1, p. 131-8 and Nat. Rev. Microbiol., 2008, 6, 4, p. 265-75). Therefore PI3K inhibitors may have anti-viral properties in addition to more established oncolytic and anti-inflammatory indications. These antiviral effects raise interesting prospects in viral induced inflammatory exacerbations. For example, the common cold human rhinovirus (HRV) is responsible for more than 50% of respiratory tract infections but complications of these infections can be significant in certain populations. This is particularly the case in respiratory diseases such as asthma or chronic obstruction pulmonary disease (COPD). Rhinoviral infection of epithelial cells leads to a PI3K dependent cytokine and chemokine secretion (J. Biol. Chem., 2005, 280, 44, p. 36952). This inflammatory response correlates with worsening of respiratory symptoms during infection. Therefore PI3K inhibitors may dampen an exaggerated immune response to an otherwise benign virus. The majority of HRV strains infect bronchial epithelial cells by initially binding to the ICAM-1 receptor. The HRV-ICAM-1 complex is then further internalised by endocytosis and it has been shown that this event requires PI3K activity (J. Immunol., 2008, 180, 2, p. 870-880). Therefore, PI3K inhibitors may also block viral infections by inhibiting viral entry into host cells.
PI3K inhibitors may be useful in reducing other types of respiratory infections including the fungal infection aspergillosis (Mucosal Immunol., 2010, 3, 2, p. 193-205). In addition, PI3Kδ deficient mice are more resistant towards infections by the protozoan parasite Leishmania major (J Immunol., 2009, 183, 3, p. 1921-1933). Taken with effects on viral infections, these reports suggest that PI3K inhibitors may be useful for the treatment of a wide variety of infections.
PI3K inhibition has also been shown to promote regulatory T cell differentiation (Proc. Natl. Acad. Sci. USA, 2008, 105, 22, p. 7797-7802) suggesting that PI3K inhibitors may serve therapeutic purposes in auto-immune or allergic indications by inducing immuno-tolerance towards self-antigen or allergen. Recently the PI3Kδ isoform has also been linked to smoke induced glucocorticoid insensitivity (Am. J. Respir. Crit. Care Med., 2009, 179, 7, p. 542-548). This observation suggests that COPD patients, which otherwise respond poorly to corticosteroids, may benefit from the combination of a PI3K inhibitor with a corticosteroid.
PI3K has also been involved in other respiratory conditions such as idiopathic pulmonary fibrosis (IPF). IPF is a fibrotic disease with progressive decline of lung function and increased mortality due to respiratory failure. In IPF, circulating fibrocytes are directed to the lung via the chemokine receptor CXCR4. PI3K is required for both signaling and expression of CXCR4 (Int. J Biochem. and Cell Biol., 2009, 41, p. 1708-1718). Therefore, by reducing CXCR4 expression and blocking its effector function, a PI3K inhibitor should inhibit the recruitment of fibrocytes to the lung and consequently slow down the fibrotic process underlying IPF, a disease with high unmet need.
PI3Kα and PI3Kβ play an essential role in maintaining homeostasis and pharmacological inhibition of these molecular targets has been associated with cancer therapy (Maira et al., Expert Opin. Ther. Targets, 2008, 12, 223).
PI3Kα is involved in insulin signaling and cellular growth pathways (Nature, 2006, 441, 366). PI3Kδ isoform-selective inhibition is expected to avoid potential side effects such as hyperglycemia, and metabolic or growth disregulation.
Selective compounds to modulate PI3Kγ are being developed by several groups as immunosuppressive agents for autoimmune disease (Nature Reviews, 2006, 5, 903-918). Of note, AS 605240, a selective PI3Kgamma inhibitor, has been shown to be efficacious in a mouse model of rheumatoid arthritis (Nature Medicine, 2005, 11, 936-943) and to delay onset of disease in a model of systemic lupus erythematosis (Nature Medicine, 2005, 11, 933-935).
There is a need to provide new PI3K inhibitors that are good drug candidates. In particular, compounds disclosed herein should bind potently to PI3K whilst showing little affinity for other receptors and show functional activity as inhibitors. They should be well absorbed from the gastrointestinal tract, be metabolically stable and possess favorable pharmacokinetic properties. When targeted against receptors in the central nervous system they should cross the blood brain barrier freely and when targeted selectively against receptors in the peripheral nervous system they should not cross the blood brain barrier. They should be non-toxic and demonstrate few side-effects. Furthermore, the ideal drug candidate will exist in a physical form that is stable, non-hygroscopic and easily formulated. The compounds disclosed herein show a certain level of selectivity against the different paralogs PI3K α, β, γ and δ. In particular, show a certain level of selectivity for the isoform PI3Kδ.
The compounds disclosed herein are therefore potentially useful in the treatment of a wide range of disorders, particularly disorders including but not limited to autoimmune disorders, inflammatory diseases, allergic diseases, disease or infection associated immunopathologies, airway diseases, transplant rejection, cancers of hematopoietic origin or solid tumors.
The invention also relates to the treatment, either alone or in combination, with one or more other pharmacologically active compounds, includes methods of treating conditions, diseases or disorders in respiratory diseases including asthma, chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF); viral infections including viral respiratory tract infections and viral exacerbation of respiratory diseases such as asthma and COPD; non-viral respiratory infections including aspergillosis and leishmaniasis; allergic diseases including allergic rhinitis and atopic dermatitis; autoimmune diseases including rheumatoid arthritis and multiple sclerosis; inflammatory disorders including inflammatory bowel disease; cardiovascular diseases including thrombosis and atherosclerosis (Future Med. Chem., 2013, 5, 4, 479-492; Biochemical Society Transactions, 2004, 32, 378); hematologic malignancies; neurodegenerative diseases; pancreatitis; multiorgan failure; kidney diseases; platelet aggregation; cancer; sperm motility; transplantation rejection; graft rejection; lung injuries; and pain including pain associated with rheumatoid arthritis or osteoarthritis, back pain, general inflammatory pain, post hepatic neuralgia, diabetic neuropathy, inflammatory neuropathic pain (trauma), trigeminal neuralgia and Central pain; hematologic malignancies such as Acute Myeloid leukaemia (AML) Myelo-dysplastic syndrome (MDS) myelo-proliferative diseases (MPD), Chronic Myeloid Leukemia (CML), T-cell acute lymphoblastic leukaemia (T-ALL), B-cell chronic lymphocytic leukemia (B-CLL), B-cell Acute Lymphoblastic leukaemia (B-ALL), follicular B-cell non-Hodgkin lymphoma (FL), relapsed small lymphocytic lymphoma (SLL), Non Hodgkins Lymphoma (NHL) B-cell lymphoma and solid tumors, such as breast cancer and lung cancer.